Plant nutrients from wastewater

They are showcasing their work at Fraunhofer's stand at the IFAT ENTSORGA fair (September 13-17 in Munich, Germany).

Plants cannot thrive without nutrients such as nitrogen, phosphorus or potassium, therefore farmers usually use organic and industrially manufactured mineral fertilizers to supply wheat, maize and others with these vital substances. In future, the need for nutrients will be soaring because we will only be able to supply the world's growing population with food and cover surging demands for biofuels by using fertilizers. Logically, that causes the prices for these nutrients to skyrocket. But that is not the only problem. The deposits of rock phosphates required for manufacturing phosphate fertilizers are becoming increasingly scarce. The researchers at the Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB in Stuttgart, Germany are working at alternatives. They want to recover these essential nutrients from wastewater.

Dr.- Ing. Maria Soledad Stoll points out that "These nutrients are hardly recovered these days." For instance, conventional municipal waste treatment plants use aluminum or ferrous salts to remove the valuable phosphate. Ms. Stoll goes on to say, "However, aluminum and iron phosphate salts can be toxic for plants even in slight concentrations, which is why they cannot be used as fertilizers." The researchers at the Fraunhofer Institute for Interfacial Engineering and Biotechnology are devising alternative methods for recovering the nutrients from the wastewater to use them for agriculture.

"We are working at new methods to recover magnesium-ammonium-phosphate and organic phosphorus from wastewater. The nutrients will then be directly marketed as a fully adequate product and used in agriculture again depending upon the properties of the soils and cultivated plants," says Ms. Stoll.